Process for synthesizing pyran nitriles

Abstract

The present invention relates to a process for synthesizing pyran nitriles of the general formula ##STR1## consisting of reacting aliphatic 1,5 hydroxyketones with aliphatic nitriles in the presence of basic substances such as oxides, hydroxides, and carbonates of alkali metal and alkaline earth metals, and in particular of alkali metal hydroxides or alcoholates, as the catalyst.

We claim: 
     
       1. A process for synthesizing pyran nitriles of the formula (I): ##STR5## wherein R 1  is alkyl and each of R 2 , R 3 , R 4 , R 5 , R 6  and R 7  is hydrogen or alkyl which consists of reacting an aliphatic 1,5-hydroxyketone of the formula (II): ##STR6## wherein R 1 , R 2 , R 3 , R 4 , R 5  and R 6  are as defined above with an aliphatic nitrile of the formula R 7  -CH 2  CN wherein R 7  is hydrogen or alkyl in the presence of an alkali metal or alkaline earth metal hydroxide or alcoholate at a temperature between 30° C. and 150° C. and wherein the molar ratio of aliphatic nitrile to hydroxyketone is between 2 and 100. 
     
     
       2. A process as claimed in claim 1 wherein the quantity of said alkali metal or alkaline earth metal hydroxide or alcoholate is between 1 and 20 mol % of the initial hydroxyketone. 
     
     
       3. A process as claimed in claim 1 wherein said molar ratio of aliphatic nitrile to hydroxyketone is between 5 and 30. 
     
     
       4. A process as claimed in claim 1 wherein said reaction temperature is between 50° and 120° C. 
     
     
       5. A process as claimed in claim 1 wherein on termination of the reaction, both the unconverted hydroxyketone and the formed pyran nitrile are removed by distillation, and the distillation residue is recycled to the feed stream for the pyran nitrile preparation reaction.